ScoreCachingWrappingScorer.cs

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/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;

namespace Lucene.Net.Search
{
    
    /// <summary> A <see cref="Scorer" /> which wraps another scorer and caches the score of the
    /// current document. Successive calls to <see cref="Score()" /> will return the same
    /// result and will not invoke the wrapped Scorer's score() method, unless the
    /// current document has changed.<br/>
    /// This class might be useful due to the changes done to the <see cref="Collector" />
    /// interface, in which the score is not computed for a document by default, only
    /// if the collector requests it. Some collectors may need to use the score in
    /// several places, however all they have in hand is a <see cref="Scorer" /> object, and
    /// might end up computing the score of a document more than once.
    /// </summary>
    public class ScoreCachingWrappingScorer:Scorer
    {
        
        private Scorer scorer;
        private int curDoc = - 1;
        private float curScore;
        
        /// <summary>Creates a new instance by wrapping the given scorer. </summary>
        public ScoreCachingWrappingScorer(Scorer scorer):base(scorer.Similarity)
        {
            this.scorer = scorer;
        }
        
        public /*protected internal*/ override bool Score(Collector collector, int max, int firstDocID)
        {
            return scorer.Score(collector, max, firstDocID);
        }

        public override Similarity Similarity
        {
            get { return scorer.Similarity; }
        }

        public override float Score()
        {
            int doc = scorer.DocID();
            if (doc != curDoc)
            {
                curScore = scorer.Score();
                curDoc = doc;
            }
            
            return curScore;
        }
        
        public override int DocID()
        {
            return scorer.DocID();
        }
        
        public override int NextDoc()
        {
            return scorer.NextDoc();
        }
        
        public override void  Score(Collector collector)
        {
            scorer.Score(collector);
        }
        
        public override int Advance(int target)
        {
            return scorer.Advance(target);
        }
    }
}